Rifles used for precision long range shooting, whether for military, law enforcement, hunting, or target shooting, often employ high power telescopic sights or riflescopes that provide a magnified image of the target, with crosshairs or another reticle at the same focal distance as the image. Other than the reticle, the riflescope provides a clear optical path that provides the shooter with a much clearer image of the target area than does the naked eye. Such riflescopes are generally elongated and compact compared to the dimensions of the rifle, so that they do not add excessive bulk and weight to the rifle. For longer ranges, higher magnifications are often employed.
A significant limitation of shooting accuracy is presented by unsteadiness of the rifle. Bench-rest competition shooters employ stable platforms for their rifles to remove this source of motion. However, most other shooters must content with imperfect supports for their rifles, with a standing shooter hand-holding a rifle being a relatively unstable condition for example. With accurate rifles capable of accuracies of better than one minute of angle or about one inch per hundred yards, even slight movements of the rifle can lead to inaccuracies far in excess of the capability of the rifle. Even a shift of only 0.01 inch by the muzzle of the rifle can generate such a significant inaccuracy. Moreover, factors such as wind and the shooter's breathing and heartbeat can generate such deviations in aim. In a combat or hunting context, the shooter's physiological responses to stress or excitement can significantly worsen the motion associated with holding an imperfectly-supported rifle.
The motion or shake that causes shooting inaccuracy also presents a visual problem. High-powered riflescopes magnify the motion, blurring the image. This makes it difficult to detect, acquire, and identify targets. A shooter might prefer a higher-powered rifle scope for accuracy, except that the shaky image in actual use makes such magnification impractical.
For weapon systems where optical acuity, bulk, weight, and power consumption do not appear to be concerns, it has been proposed to employ a gyroscopically-stabilized television image as a fire-control sighting system for a weapon on a moving platform to provide a still image. This is described in U.S. Pat. No. 3,659,494 to Philbrick et al. The Philbrick system projects an image of the target on a photodetector, which converts the image into an electronic signal. An electron beam regenerates the image on a phosphor screen that is viewed by the user. The regenerated image is stabilized by a facility that shifts the electron beam based on gyroscopic inputs. While apparently suitable for aiming large weapon systems, it does not appear to be suitable for applications where a high quality image, and small size, low weight, low cost, and simplicity are desired. Moreover, it appears unsuited to adapt to existing rifle scopes.
The Philbrick patent further describes the system applied to a weapon with an electronic trigger system, so that the sighting system itself automatically sends an electronic signal that fires the weapon when the sight is in a neutral or “home” position in which the image is not shifted, unless the user inhibits firing by releasing pressure on a trigger solenoid. Thus, the Philbrick system is further unsuitable for adaptation to convention rifles using mechanical triggers.